The present invention generally relates to tractors having a tractor cab, and more particularly relates to an apparatus and method for moving a tractor cab relative to a tractor body.
Material handling machines, such as grapple tractors (hereinafter referred to as tractors), are typically used in projects which require the movement of significant amounts of scrap, such as ferrous materials. These types of tractors generally include a grapple or magnet operatively linked to a boom and arm. Hereinafter, the boom and arm is collectively referred to as the grapple arm. The primary function of the grapple arm is to move the grapple in such a manner that it can grasp and transfer the scrap from one location to another. These types of tractors also include a cab that houses the operator and the controls used to direct the movements of the grapple arm, and therefore the grapple.
These tractors are often used to load or unload scrap from truck beds or from barges. However, using such tractors to perform the aforementioned loading or unloading function has a significant drawback. That is, it is very difficult for the operator of the tractor to see down into the truck bed or barge from his or her position in the cab. The operator'inability to see down into the truck bead or barge impedes his or her ability to properly control the movement of the grapple arm and grapple. As a result, the operator's ability to efficiently operate the grapple arm and grapple decreases.
In order to overcome the above described problem, several tractor models are constructed to include an adjustable cab riser apparatus. Such an apparatus allows the operator of the tractor to raise the cab to the desired height above the tractor body. Having the cab positioned at an appropriate height above the tractor body allows the operator to see into the truck bed, barge or container being loaded or unloaded, and therefore facilitates the proper control of the grapple arm and grapple.
Some cab riser apparatus are constructed to include a large unitary bracket member directly welded onto the frame of the tractor body. These apparatus also include a hydraulic cylinder and a number of support arms. The hydraulic cylinder and support arms are connected to the bracket member and a brace. The brace is connected to a platform member for supporting the tractor cab. Generally, the aforementioned cab riser components are arranged such that the actuation and extension of the hydraulic cylinder causes the brace, platform member, and therefore the tractor cab, to rise above the tractor body to a desired height. However, as will be discussed below, present cab riser apparatus suffer from several drawbacks.
One problem with the above described arrangement is that the hydraulic cylinder is less stable in its extended position, as compared to when it is in its retracted position. For example, in its extended position the hydraulic cylinder has a greater tendency to move about or "wobble" due to forces it encounters during use of the tractor. Since the hydraulic cylinder is attached to the platform member via the brace, its decreased stability is communicated to the platform member, and thus the cab. Therefore, the cab, in its raised position, also has a tendency to move about or "wobble" during use of the tractor.
Another problem with certain types of cab riser apparatus relates to the position of the cab once it is raised above the tractor body. For example, the spatial relationship of the support arms, bracket and brace typically causes the platform member to tilt relative to the tractor body when moved to an elevated position. Since the platform member supports the cab, the cab also tilts when moved to an elevated position. The tilting of the cab can be distracting or uncomfortable for the operator of the tractor.
Additional problems with prior art cab riser apparatus include (1) their inability to be retrofit onto existing tractor frames; (2) they are relatively bulky, and thus require a significant amount of space; and (3) the use of a large unitary bracket member is difficult to fabricate, and then weld onto a frame of the tractor body.
Therefore, in light of the above discussion, it is apparent that a cab riser apparatus that addresses the above described problems is desirable. The present invention provides such an apparatus. The cab riser apparatus of the present invention utilizes a number of "inverted hydraulic cylinders" and support arms arranged in a parallelogram linkage between a brace and a bracket member to elevate a tractor cab.
In use, the cab riser of the present invention provides an apparatus for elevating a cab which is relatively stable and thus inhibits the cab's movement during use of the tractor. Moreover, the present invention provides a cab riser apparatus wherein the cab does not tilt relative to the tractor body when located in any elevated position. In addition, the present invention provides a cab riser apparatus which (1) can be retrofit onto existing tractor bodies; (2) is relatively compact and thus requires less space when mounted; and (3) utilizes a bracket assembly which is relatively easy to fabricate, and then mount onto a tractor body.